1. Field
The present application relates to an internal-combustion-engine supercharger.
2. Description of the Related Art
A conventional internal-combustion-engine supercharger of a vehicle is disclosed in Japanese Unexamined Patent Application Publication No. 07-279677. In the technique disclosed therein, a bypass passage for recirculating intake air that is compressed by a radial centrifugal force generated by rotation of an impeller is provided. Furthermore, a control valve for controlling the recirculation flow rate of the intake air is provided at an intermediate point of the bypass passage.
Superchargers are being reduced in size and increased in response rate to eliminate turbo lag. Under the circumstances, if an impeller is rotated by a driving force, it cannot compress the intake air and idles, causing a surge. A bypass passage eliminates a surge by recirculating intake air compressed by the supercharger into intake air to be taken in before compression.